The Mysterious Gotland Grooves

Feb 23, 2017 5 comments

Scattered throughout the island of Gotland, in the middle of the Baltic Sea, are thousands of stones with strange grooves or furrows cut into its smooth, hard surface. The grooves always occur in groups, cut side by side and are of varying length, width and depth.

At first glance, it appears as if someone had been sharpening their axes or swords on them. That was the general opinion when the grooves were widely reported in the mid-19th century. Consequently, the grooves were called "sharpening stones". But soon scholars began to have doubts about their origin, since the shape and size of the grooves made them unfit for sharpening swords. Someone pointed out that stone-age swords, and even those from the Middle Ages and Viking Age, were too wide to fit into the grinding grooves.


Photo credit: Sören Gannholm

Another evidence —or rather, the lack of it— that didn’t fit into the puzzle was the complete lack of stone axes and other weapons that were supposedly sharpened in the stones, in its vicinity. Archeologists have failed to retrieve any remnants of stone axes, and other waste, even at places which have been described as veritable ‘sword sharpening workshops’.

Gotland is not alone with these strange marks in granite and limestone rocks. Grooves have been found at many places across Europe such as in Norway, Finland, France, Luxembourg and England, and as far away as in Australia and India. In France, the grooves have been dated to the Neolithic period, and are called polissoirs. They were made by the same culture who built dolmens (rock tombs) and erected menhirs (standing stones). But nowhere else grinding grooves occur in such large number and concentration as in Gotland. They are spread across virtually the entire island. They are found carved in isolated boulders, in the bedrock and in limestone outcrops.

Since the American astronomer Gerald Hawkins suggested that the Stonehenge could have had an astronomical function, scholars have been trying to find an astronomical connection with virtually any stone age antique they can’t explain. The grooves of Gotland are no different. Archeologists are now wondering whether the answer to the mystery lies in the alignment of the grooves. Many of the grooves do appear to align towards certain celestial bodies, such as the sun or the moon.

The orientation of the grooves have been interpreted differently by different scholars. Some believe that the grooves are some kind of a lunar calendar, while others offer simple explanation— people turned in certain directions in order not to get the sun in the eyes when grinding.

So far, more than 3,600 grinding grooves have been discovered in Gotland, of which about 700 occur in the solid limestone outcrop and the rest are divided among about 800 blocks.


Photo credit: Sören Gannholm


Photo credit: Sören Gannholm


Photo credit: Sören Gannholm

Sources: Sören Gannholm / Wikipedia


  1. How about stripping bark from branches for shaping handles or shafts etc. Second thought is for processing stalks for extracting juices or sap.

  2. Taking Leo's comment one step further, the shape and color of the grooves suggest sharpening stones for fire-hardened spear tips.

  3. Gotland was glaciated, so this could simply be glacial striations.

  4. Maybe they just pulled out orthoceras fossils.

  5. Or the area was good for mining or just smelting and they made blanks to be honed in another location. They look to be of different sizes and such.


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